Last week I was talking about how Cognac is made from blending several eaux de vie together to produce a consistency of taste. The actual process of how this happens is a fascinating one and one, I discovered, that needs a very skilled palate.

In the town of Cognac, on the banks of the Charente River, are the vast warehouses of Hennessy, the largest of all the Cognac houses. Like many of the drinks industries in France it has Irish roots, going back to 1765 when Richard Hennessy from Co. Cork set up his firm trading in eau de vie in Cognac after serving in the army of Louis XV. Hennessy's warehouses are huge, and in them their eaux de vie - the unblended spirits - age in barrels of Limousin oak. Each barrel has beautiful calligraphy done in chalk that mark the barrel's year, it's region of Cognac, the grower and the distillery that created it from the white Charente wine. Some of these barrels are very old - in one warehouse most of the years from 1900 to 1950 are represented and using a 'fusil' - a small glass receptacle which can be lowered through the barrel's bung hole, we got to taste the 1900.

These spirits age and mature in the oak barrels partly by absorbing essences from the wood and also by losing a lot of their alcohol through evaporation. Older spirits are darker and more mellow than the fiery new ones. When the tasters and blenders think the spirit has achieved the perfect maturation it's transferred to glass demijohns where no more evaporation or change can take place. These very old spirits - dating back as far as 1800 - are used in the blending of the top of the range Cognacs like 'Richard', named after the firm's founder.

The task of the blending team is to taste all the different years, the different areas, the different growers which are all aged separately, and to blend these varying tastes into a recognisable house style. Ten of us sat in a small room with only three different eaux de vie, a lively and fresh 1983; a flowery, pale and scented 1978; a 1970 full of smoke and toffee and tried to blend them into a Cognac. It's a task that's far harder than you can imagine, I have huge respect for the blending team who blend their Cognacs with upwards of 100 eaux de vie to obtain the desired blend. That team is led by Yann Fillioux, the seventh generation of the Fillioux family to be Master Blender.

If you wonder why old Cognac is so expensive here's something to bear in mind. It takes 9 barrels of wine to make one barrel of eau de vie. To have just one barrel of 100 year old eau de vie, 9 barrels worth will have evaporated, so you could say it takes 90 barrels of wine to make one 100 year old barrel of aged spirit.

Wine of the Week

Oracle Cabernet Sauvignon, 2001

The Oracle range of varietals from South Africa has just landed, a Cabernet, a Shiraz, a Sauvignon Blanc and a Chardonnay. All four come in a handsome wide-shouldered bottle, have a proper metal capsule and good-quality labelling giving the wines an expensive feel in the hand. The joy is that they're not expensive, the Cabernet in particular tasting more like a wine that's twice its price. Full of New World fruit, but with enough backbone to be interesting.

Widely available, RRP €7.99